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第52卷第2期表面技术2023年2月SURFACE TECHNOLOGY·297·石墨表面TaC涂层的熔盐法制备及表征董天下1，孟凡桂1，陈红梅2,3，张九阳4，高超4，王宗玉4（1.中南林业科技大学 材料科学与工程学院，长沙 410004；2.湖南人文科技学院 精细陶瓷与粉体材料湖南省重点实验室，湖南 娄底 417000；3.湖南涉外经济学院，长沙 410205；4.山东天岳先进科技股份有限公司，济南 250000）摘要：目的以K2TaF7和Ta粉为主要原料，在石墨材料表面制备TaC涂层。
方法反应物在1 200 ℃的熔盐体系中保温3 h，反应生成碳化物，经后续2 300 ℃真空保温1 h后，得到TaC涂层材料。
采用XRD和SEM对涂层的组成结构进行表征，采用拉开法对涂层的和石墨基体的结合强度进行测量，采用纳米压痕对涂层的硬度和弹性模量进表征，最后对TaC涂层的抗腐蚀性能进行模拟测试评估和实际的SiC 长晶测试。
结果熔盐法制备的TaC涂层连续地覆盖在石墨表面，保持了原始石墨的形貌，其物相组成为TaC，呈现出亮黄色，厚度为20~40 μm，涂层的晶粒无择优取向生长，呈现出无序堆积的状态。
TaC 涂层与石墨基体的结合强度为9.49 MPa，硬度和弹性模量分别为14.42 GPa和123.32 GPa。
TaC涂层样品于2 300 ℃的SiC腐蚀气氛环境下保温3 h，质量损失率仅为0.01 g/(m2·h)，远低于同测试条件下无涂层石墨样品的质量损失率4.67 g/(m2·h)。
在2 300 ℃氩气气氛下保温3 h的SiC粉包埋TaC涂层的接触腐蚀试验中，SiC和TaC涂层的界面清晰，没有发生相互的扩散。
TaC涂层部件应用于2 000 ℃以上保温150 h以上的SiC单晶的生长制备后，涂层部件总体形貌保持完整，部件边缘棱角区域出现了脱落，但其他部位的TaC涂层仍和基体结合良好，涂层在长晶过程中的质量损失率约为0.41 g/(m2·h)，表现出良好的抗腐蚀性能。
aloh3与co2反应方程式介绍在化学反应中，不同物质之间的相互作用可以引发多种有趣的变化。
本文将探讨氢氧化铝（Al(OH)3）与二氧化碳（CO2）之间的反应方程式以及相关的化学性质和应用。
反应方程式氢氧化铝与二氧化碳的反应方程式如下所示：2 Al(OH)3 + 3 CO2 → Al2(CO3)3 + 3 H2O这个方程式描述了氢氧化铝和二氧化碳反应生成碳酸铝和水的过程。
在这个反应中，氢氧化铝的两个分子与三个二氧化碳分子反应，生成一个碳酸铝分子和三个水分子。
反应机理氢氧化铝与二氧化碳反应的机理涉及各种中间产物和反应步骤。
下面是一种可能的反应机理：1.首先，氢氧化铝分子中的氢氧根离子（OH-）与二氧化碳分子中的碳酸根离子（CO32-）发生亲核取代反应，形成一个中间产物：碳酸铝的氢氧根盐（Al(OH)(CO3)）。
2.接下来，碳酸铝的氢氧根盐进一步与氢氧化铝分子发生反应，生成碳酸铝（Al2(CO3)3）和水（H2O）。
这个反应机理是基于实验观察和理论推断的，具体的细节可能还需要进一步的研究和验证。
化学性质氢氧化铝（Al(OH)3）氢氧化铝是一种白色固体，常见的形式是无定形粉末或结晶体。
它具有吸湿性和碱性，可以与酸反应生成盐和水。
在与二氧化碳反应时，氢氧化铝可以中和二氧化碳的酸性，形成碳酸盐。
二氧化碳（CO2）二氧化碳是一种无色无味的气体，在常温下是稳定的。
它是一种重要的温室气体，也是植物进行光合作用的关键成分之一。
与氢氧化铝反应时，二氧化碳可以与氢氧化铝的氢氧根离子发生反应，产生碳酸盐。
碳酸铝（Al2(CO3)3）碳酸铝是一种白色固体，常见的形式是无定形粉末或结晶体。
它是一种稳定的化合物，可以用作材料科学和化学工程中的原料。
碳酸铝也是一种可溶于水的盐，可以与酸反应生成相应的金属盐和二氧化碳。
应用氢氧化铝与二氧化碳的反应在工业和实验室中具有一定的应用价值。
工业应用碳酸铝是一种重要的工业原料，广泛应用于陶瓷、玻璃、纸张和橡胶等行业。
三氯化六氨合钴实验现象解释三氯化六氨合钴，常用的化学试剂之一，是一种暗红色结晶物质，也称作氰化钴（III）盐。
在化学实验中，它常用于检测铁离子或铜离子的存在，并可用于气体检测，催化剂制备等。
其化学式为 [Co(NH3)6]Cl3，分子量为267.5。
实验现象：将三氯化六氨合钴溶于水中时，溶液呈现出红色，当加入氨水后，溶液颜色由红转为深蓝色，放置一段时间后，深蓝色溶液会逐渐变为浅蓝色，最终慢慢变为粉色。
解释：三氯化六氨合钴的红色溶液是由于配合物[Co(NH3)6]3+的颜色引起的。
在配合物中，铵离子作为配体，与铵离子形成包围金属离子的八面体结构，从而形成了三氯化六氨合钴的复合物。
这个配合物呈现红色，属于吸收绿色光的背景，从而使红色光被反射和传播。
当加入氨水后，会发生反应，生成[Co(NH3)6]2+ 配合物。
这个配合物由氨分子包围六个铵离子和一个钴离子，会使得该化合物的分子体积更大，这样就会使它吸收与[Co(NH3)6]3+ 配合物不同的波长的光，由红色变成更深的蓝色。
此外，三氯化六氨合钴的盐酸根离子(HCl)也会从溶液中分离，且生成的氯化钴离子会使溶液的酸度降低，从而使[Co(NH3)6]2+ 的酸-碱指数发生变化，使其吸收不同的波长。
慢慢深蓝色的配合物溶液会在空气中发生氧化反应，发生了一系列氧化还原反应，氨分子逐渐分解，生成一些氮气和氢气气泡，在溶液中释放出了氢离子，这些氢离子能作为邻近氨分子的酸基而影响其配位性质。
氧气会在配合物溶液中催化反应，使得氢氧化钴离子生成，由于其水溶性不佳，逐渐从溶液中析出，溶液变浅蓝色。
随后，氢氧化钴离子不断发生水解反应，最终形成了一种粉色的物质，这是水合铵离子的染色。
参考文献：1. Swati Anand, Jainendra Jain. A simple method for the preparation of Co(NH3)63+ and its use as chiral selector[J]. Journal ofChromatography A, 2002, 958(1-2):289-295.2. Sun D, Duan Y, Li X, et al. Preparation and Characterization of Co(NH3)63+@TiO2Hybrids with Enhanced Photocatalytic Activity[J]. ChemistrySelect, 2017, 2(18): 5106-5111.3. Roger L. DeKock, David E. Drown. A Study of the Resonance AbsorptionSpectrum of Tris(ethylenediamine)cobalt(III) Ion[J]. Journal of the American Chemical Society, 1955, 77(1): 246-251.。
第 50 卷 第 4 期2021 年 4 月Vol.50 No.4Apr. 2021化工技术与开发Technology & Development of Chemical Industry化学法去除废水中镉的研究进展李唯艳，蒋 鑫，任建军，徐 倩，蔡华敏，贾冬梅（滨州学院化工与安全学院，山东 滨州 256603）摘 要：镉作为一种重金属，毒性较强，对人类和生态环境会产生严重危害。
本文概述了不同含镉废水的化学法处理技术的特点及应用，展望了含镉废水处理技术的发展方向。
关键词：镉；重金属；化学法；沉淀法中图分类号：X 703.1 文献标识码：A 文章编号：1671-9905(2021)04-0046-03通信联系人：贾冬梅，教授，研究方向为工业污水资源化。
E-mail:*****************收稿日期：2020-12-23镉（Cd）具有良好的韧性和延展性，其合金及化合物在工业生产中被广泛应用。
环境中镉的来源主要有镉矿、镉冶炼厂、电镀，以及用镉化合物作原料或触媒的工厂产生的废水、废渣等。
镉的毒性高，可在生物体内富集，会通过食物链进入人体而引起慢性中毒[1]。
因此，废水中的镉在排放前必须进行有效处理。
目前，含镉废水的处理方法有膜分离法、吸附法、生物法、沉淀法、电絮凝法及离子交换法等[2]。
1 化学法除镉1.1 化学沉淀法化学沉淀法是一种传统的水处理方法，由于其技术成熟、容易控制，在国内外的重金属废水处理中被广泛使用。
沉淀法是在含镉废水中加入沉淀剂，使其发生化合反应，生成Cd(OH)2、CdS、CdCO 3等镉的沉淀物。
常用的沉淀剂有氢氧化物、聚合氯化铝、聚合硫酸铁、碳酸盐等。
聚合硫酸铁对镉主要起絮凝共沉作用[3]。
郭崇武等[4]用二甲基二硫代氨基甲酸钠处理含镉废水，研究发现，在pH 为2~9范围内，镉离子的去除效率最高，出水中镉的浓度能够满足GB 21900−2008《电镀污染物排放标准》，但在处理过程中应严格控制氨三乙酸等配位剂的初始浓度。
简历个人简介：熊杰，男，副教授，1979年7月出生于四川大竹，2002年7月电子科技大学应用化学本科毕业，2007年6月获电子科技大学材料物理化学专业博士学位，同年6月留电子科技大学微电子与固体电子学院工作。
2009年5月-2010年5月在美国Los Alamos国家实验室超导中心（Superconductor Technology Center）从事博士后研究，2010年5月-2011年5月美国Los Alamos国家实验室综合纳米技术中心（Center for Integrated Nanotechnology）助理研究员，2011年5月至今美国Los Alamos国家实验室综合纳米技术中心Guest Scientist。
现为美国材料研究协会（MRS），美国真空协会（AVS），美国物理学会（APS），美国电气和电子工程师协会（IEEE）会员。
近年来，在多元氧化物功能薄膜材料以及能源材料领域进行了比较系统深入的研究，主持和参加了包括国家自然科学基金，科技部863，总装预研，美国能源部（DOE）LDRD项目等多项国家省部级科研项目，迄今在包括Nature Communication，Advanced Materials，Applied Physics Letters, Journal of Applied Physics等国内外著名刊物上发表研究论文50余篇，其中已被SCI/EI检索40余篇，撰写英文专著（章节）2部。
在国内外学术会议及学术机构做学会报告30余次，获国防科技进步三等奖一项。
担任国际期刊the International Journal of Material Science（IJMS）联合主编（Co-Editor-in-Chief），并为多家国际学术期刊的审稿人。
专著：1)J Xiong, B Tao and Y Li, “Sputter deposition of large-area double-sided YBCOsuperconducting films”, in High temperature superconductors, edited by X G Qiu, (Woodhead Publishing Limited, 2011)2) B.W. Tao, J. Xiong and X.Z. Liu, “High Rate Deposition of Double-sided YBCO Thin Filmswith Sputtering”, in Superconducting Thin Films: New Research, edited by Arnold H.Burness, (Nova Science Publishers, 2008, 3rd Quarter)主要论文：1)G.F. Zou, H.M. Luo, S. Baily, Y.Y. Zhang, N.F. Haberkorn, J. Xiong, E. Bauer, T.M.McCleskey, A.K. Burrell, L. Civale, Y.T. Zhu, J.L. MacManus-Driscoll & Q.X. Jia, Highly aligned carbon nanotube forests coated by superconducting NbC, Nature Communications, Vol. 2, 428 (2011)2)Park, Bae Ho, Li Y.R., Xiong J., Jia Q.X., Dielectric properties of epitaxial Ba1-xSrxTiO 3films on MgO substrates, Functional Materials Letters, Vol.4, 41 (2011)3) E.-M. Choi, S. Patnaik, E. Weal, S.-L. Sahonta, H. Wang, Z. Bi, J. Xiong, M. G. Blamire,Q. X. Jia, and J. L. MacManus-Driscoll, Strong room temperature magnetism in highly resistive strained thin films of BiFe0.5Mn0.5O3, APPLIED PHYSICS LETTERS, V ol. 98, 012509 (2011)4)Xiong J, Qin WF, Y u M, Tao BW, Zhang N, Zhang F, Feng X, Song XK, Li YR, Singlecerium zirconate buffer layer on biaxially textured metal substrates for high performance coated conductors, JOURNAL OF MA TERIALS SCIENCE, V ol. 46, 238 (2011)5)Xiong J, Matias V, Wang H, Zhai JY, Maiorov B, Trugman D, Tao BW, Li YR, and JiaQX, Much simplified IBAD-TiN template for high performance coated conductors, JOURNAL OF APPLIED PHYSICS, V ol. 108, 083903 (2010)6)Zou GF, Luo HM, Zhang YY, Xiong J, Wei QM, Zhuo MJ, Zhai JY, Wang HY, WilliamsD, Li N, Bauer E, Zhang XH, McCleskey TM, Li YR, Burrell AK, Jia QX, A chemical solution approach for superconducting and hard epitaxial NbC film, CHEMICAL COMMUNICA TIONS, V ol.46, 7837 (2010)7)Zhang YY, Sheehan CJ, Zhai JY, Zou GF, Luo HM, Xiong J, Zhu YT, Jia QX,Polymer-Embedded Carbon Nanotube Ribbons for Stretchable Conductors, ADV ANCED MA TERIALS, V ol.22, 3027 (2010)8)Cheng L , Wang X, Y ao X, Wan W, Li FH, Xiong J, Tao BW, Jirsa M, Enhancement ofYBCO Thin Film Thermal Stability under 1 A TM Oxygen Pressure by Intermediate Cu2O Nanolayer, JOURNAL OF PHYSICAL CHEMISTRY B, V ol.114, 7543 (2010)9)Qin WF, Xiong J, Li YR, Structure and Properties of BST/BZT/BST Multilayer Film,JOURNAL OF INORGANIC MA TERIALS, V ol.25, 247 (2010)10)Qin WF, Xiong J, Li YR, COMPARISON ON THE EFFECT OF SrRuO3 ANDLa0.5Sr0.5CoO3 BOTTOM ELECTRODE ON DIELECTRIC PROPERTIES OF Ba0.6Sr0.4TiO3 THIN FILMS PREPARED BY PULSED LASER DEPOSITION, SURFACE REVIEW AND LETTERS, V ol.16, 493 ( 2009)11)Jie Xiong, Bowan Tao, Wenfeng Qin, Xiao Feng, Xiaoke Song, Fei Zhang, Yanrong Li,Reel-to-Reel Continuous Deposition of CexZr1-xO2 Single Buffer Layer for YBCO coated conductors, Journal of Physics, 153 (2009) 01203612)Qin WF, Xiong J, Zhu J, Tang JL, Jie WJ, Wei XH, Zhang Y, Li YR, “High tunabiltyBa0.6Sr0.4TiO3 thin films fabricated on Pt-Si substrates with La0.5Sr0.5CoO3 buffer layer”, JOURNAL OF MA TERIALS SCIENCE-MA TERIALS IN ELECTRONICS, V olume: 19, Issue: 5, Pages: 429-433, MAY 200813)Xiong J, Tao BW, Qin WF, Tang JL, Han X, Li YR, “Reel-to-reel continuoussimultaneous double-sided deposition of highly textured CeO2 templates for YBa2Cu3O7-delta coated conductors” , SUPERCONDUCTOR SCIENCE & TECHNOLOGY, V olume: 21, Issue: 2, Article Number: 025016, FEB 200814)Qin WF, Xiong J, Zhu J, Tang JL, Jie WJ, Zhang Y, Li YR, “Enhanced electricalproperties of multilayer Ba(Zr0.2Ti0.8)O-3/Ba0.6Sr0.4TiO3/Ba(Zr0.2Ti0.8)O(3)thin films for tunable microwave applications” , JOURNAL OF MA TERIALS SCIENCE, V olume: 43, Issue: 1, Pages: 409-412, JAN 200815)Xiong J, Qin WF, Tang JL, Tao B, Cui XM, Li YR, “Preparation and c haracterization ofmicrocrack-free thick YBa2CU3O7-delta films”, RARE METALS, V olume: 26, Issue: 5, Pages: 403-407, OCT 200716)Xiong J, Chen Y, Qiu Y, Tao BW, Qin WF, Cui XM, Li YR, “Preparation andcharacterization of CeO2/YSZ/CeO2 buffer layers for YBCO co ated conductors” , JOURNAL OF MA TERIALS SCIENCE & TECHNOLOGY, V olume: 23, Issue: 4, Pages: 457-460, JUL 200717)Xiong J, Qin WF, Cui XM, Tao BW, Tang JL, Li YR, “Thickness-induced residualstresses in textured YBCO thin films determined by crystalline group method”, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICA TIONS, V olume: 455, Issue: 1-2, Pages: 52-57, MAY 1 200718)Xiong J, Chen Y, Qiu Y, Tao BW, Qin WF, Cui XM, Tang JL, Li YR,” Deposition ofhigh-textured buffer layers for YBCO coated conductors by all-IPA T-p rocess”, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICA TIONS, V olume: 454, Issue: 1-2, Pages:56-60, APR 15 200719)Xiong J, Qin WF, Cui XM, Tao BW, Tang JL, Li YR, “High-resolution XRD study ofstress-modulated YBCO films with various thicknesses”, JOURNAL OF C RYSTAL GROWTH, V olume: 300, Issue: 2, Pages: 364-367, MAR 15 200720)Xiong J, Qin WF, Cui XM, Tao BW, Li YR, “Fabrication of SmBa2Cu3O7 films on CeO2buffered sapphire”, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, V olume: 19, Issue: 1-2, Pages: 29-32, FEB 200621)Xiong J, Chen Y, Qiu Y, Tao BW, Qin WF, Cui XM, Tang JL, Li YR, “A novel process forCeO2 single buffer layer on biaxially textured metal substrates in YBCO coated conductors”, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, V olume: 19, Issue: 10, Pages: 1068-1072, OCT 200622)Xiong J, Qin WF, Cui XM, Tao BW, Tang JL, Li YR, “Effect of processing conditions andmethods on residual stress in CeO2 buffer layers and YBCO superconducting films”, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICA TIONS, V olume: 442, Issue: 2, Pages: 124-128, AUG 15 2006。
ORIGINAL ARTICLEPreparation and Characterization of a NovelExtracellular Polysaccharide with Antioxidant Activity,from the Mangrove-Associated Fungus Fusarium oxysporumYan-Li Chen &Wen-Jun Mao &Hong-Wen Tao &Wei-Ming Zhu &Meng-Xia Yan &Xue Liu &Tian-Tian Guo &Tao GuoReceived:1August 2013/Accepted:7January 2015/Published online:28January 2015#Springer Science+Business Media New York 2015Abstract Marine fungi are recognized as an abundant source of extracellular polysaccharides with novel structures.Mangrove fungi constitute the second largest ecological group of the marine fungi,and many of them are new or inadequate-ly described species and may produce extracellular polysac-charides with novel functions and structures that could be explored as a source of useful polymers.The mangrove-associated fungus Fusarium oxysporum produces an extracel-lular polysaccharide,Fw-1,when grown in potato dextrose-agar medium.The homogeneous Fw-1was isolated from the fermented broth by a combination of ethanol precipitation,ion-exchange,and gel filtration chromatography.Chemical and spectroscopic analyses,including one-and two-dimensional nuclear magnetic resonance spectroscopies showed that Fw-1consisted of galactose,glucose,and man-nose in a molar ratio of 1.33:1.33:1.00,and its molecular weight was about 61.2kDa.The structure of Fw-1contains a backbone of (1→6)-linked β-D -galactofuranose residues with multiple side chains.The branches consist of terminal α-D -glucopyranose residues,or short chains containing (1→2)-linked α-D -glucopyranose,(1→2)-linked β-D -mannopyranose,and terminal β-D -mannopyranose residues.The side chains are connected to C-2of galactofuranose res-idues of backbone.The antioxidant activity of Fw-1was eval-uated with the scavenging abilities on hydroxyl,superoxide,and 1,1-diphenyl-2-picrylhydrazyl radicals in vitro,and the results indicated that Fw-1possessed good antioxidant activ-ity,especially the scavenging ability on hydroxyl radicals.Theinvestigation demonstrated that Fw-1is a novel galactofuranose-containing polysaccharide with different structural characteristics from extracellular polysaccharides from other marine microorganisms and could be a potential source of antioxidant.Keywords Mangrove-associated fungus .Fusarium oxysporum .Extracellular polysaccharide .Preparation .Characterization .Antioxidant activityIntroductionMangroves grow in saline coastal sediment habitats in the tropics and subtropics harboring a great diversity of marine fungi (Shearer et al.2007).Mangrove fungi constitute the second largest ecological group of the marine fungi and may produce chemicals with novel functions and structures (Kobayashi and Tsuda 2004).Fungi often produce extracellu-lar polysaccharides that are secreted into the growth media or remain tightly attached to the cell surface (Seviour et al.1992).The research on extracellular polysaccharides from marine fungi is attempted for providing polysaccharide with novel functions and structures (Chen et al.2012;Sun et al.2011).The extracellular polysaccharides produced by marine fungi become an important research area in new drug discovery and show enormous development prospects (Kanekiyo et al.2005).Polysaccharides with hexofuranose units are of interest be-cause of their unique structures and specific properties (Leal et al.2010).The investigations showed that galactose is the most widespread hexose in furanose form in naturally occur-ring polysaccharides (Pedersen and Turco 2003;Peltier et al.2008).The galactofuranose-containing extracellularY .<L.Chen :W.<J.Mao (*):H.<W.Tao :W.<M.Zhu :M.<X.Yan :X.Liu :T.<T.Guo :T.GuoKey Laboratory of Marine Drugs,Ministry of Education,Institute of Marine Drugs and Foods,Ocean University of China,5Yushan Road,Qingdao 266003,People ’s Republic of China e-mail:wenjunmqd@Mar Biotechnol (2015)17:219–228DOI 10.1007/s10126-015-9611-6polysaccharides with novel structural characteristics have been isolated from the fermented broth or cell walls of some microorganisms(Gander et al.1974;Ikuta et al.1997;Latgéet al.1994;Unkefer and Gander1990).With today’s interest in new renewable sources of polymers,the galactofuranose-containing extracellular polysaccharides represent potential source to be explored.However,the galactofuranose-containing extracellular polysaccharides from marine fungi have not yet been fully studied.In the current study,a novel galactofuranose-containing extracellular polysaccharide was isolated from the fermented broth of the mangrove-associated fungus Fusarium oxysporum by a combination of ethanol precipitation,ion-exchange,and gel filtration chroma-tography,and its structural characterization was investigated using chemical and spectroscopic methods,including one-and two-dimensional nuclear magnetic resonance(1D and 2D NMR)spectroscopic analyses.The antioxidant activity of the extracellular polysaccharide was also evaluated by scavenging assays involving hydroxyl,superoxide,and1,1-diphenyl-2-picrylhydrazyl(DPPH)radicals.Materials and MethodsMaterialsMonosaccharides(D-glucose,L-rhamnose,D-xylose,L-arabi-nose,D-mannose,L-fucose,D-galactose,D-glucuronic acid,D-galacturonic acid,D-mannuronic acid,N-acetyl-β-D-glucos-amine),1,1-diphenyl-2-picrylhydrazyl,trifluoroacetic acid, thiobarbituric acid,trichloroacetic acid,and1-phenyl-3-meth-yl-5-pyrazolone were from Sigma-Aldrich(St.Louis,MO, USA).Pullulan standards(Mw=344,200,107,47.1,21.2, and9.6kDa)were from the Showa Denko K.K.(Tokyo, Japan).Q Sepharose Fast Flow and Sephacryl S-100were from GE healthcare(Piscataway,NJ,USA).Dialysis mem-branes(flat width,44mm;molecular weight cut-off,3500) were from Lvniao(Yantai,China).Microbial Strain and Culture ConditionsThe marine fungus F.oxysporum was isolated from fresh leaves of Ipomoea pes-caprae(Linn.)collected from South Sea,China.It was identified according to its morphological characteristics and18S rRNA sequences,and the accession number of Genbank was JN604549.Briefly,the fungus was cultivated in the liquid medium containing yeast extract(3g/ L),peptone(5g/L),glucose(20g/L),malt extract(3g/L),sea salt(24.4g/L),KH2PO4(0.5g/L),NH4Cl(0.5g/L),pH6.0–6.5,at25°C for40days,and50L of fermented broth was obtained.Preparation of the Extracellular PolysaccharideThe fermented broth was filtered through cheese cloth,the filtrate was concentrated to1/15of its original volume under reduced pressure at40°C,and a threefold of the volume of 95%(v/v)ethanol was added.The resulting precipitate was recovered by centrifugation at3600×g for10min,dialyzed in cellulose membrane tubing against distilled water for72h. The retained fraction was dried,and the protein in the fraction was removed as described by Matthaei et al.(1962).The crude polysaccharide was fractionated by anion-exchange chroma-tography using a Q Sepharose Fast Flow column(30×3cm) coupled to an AKTA FPLC system and elution with a step-wise gradient of0,0.2,and1.0M NaCl.The fractions were assayed for carbohydrate content by the phenol–sulfuric acid method.The fractions eluted with distilled water were pooled, dialyzed,and further purified on a Sephacryl S-100column (70×2cm)eluted with0.2M NH4HCO3at a flow rate of 0.3mL/min.The major polysaccharide fractions were pooled, freeze–dried,and designated as Fw-1.Determination of Purity and Molecular WeightPurity and molecular weight were determined by high-performance gel permeation chromatography(HPGPC)with a Shodex Ohpak SB804(7.8×300mm,Tokyo,Japan)column and a refractive index detector(Agilent RID-10A Series),and elution with0.1M Na2SO4at a flow rate of0.5mL/min(Li et al.2012).Of1%sample solutions in0.2M Na2SO4,20μL was injected.The molecular weight was estimated by refer-ence to a calibration curve made by pullulan standards.General AnalysisTotal sugar content was measured by the phenol–sulfuric acid method using galactose as the standard(Dubois et al.1956). Protein content was assayed according to the modified Lowry method(Bensadoun and Weinstein1976).Sulfate content was measured according to Silvestri et al.(1982).Uronic acid con-tent was determined by the carbazole–sulfuric acid method (Bitter and Muir1962).Analysis of Monosaccharide CompositionFive milligrams of polysaccharide was hydrolyzed with2M trifluoroacetic acid at100°C for6h.Excess acid was re-moved by co-distillation with methanol after the hydrolysis was completed.Sample was subjected to reversed-phase high-performance liquid chromatography(HPLC)after pre-column derivatization and UV detection(Li et al.2011). Sugar identification was done by comparison with reference sugars(D-glucose,L-rhamnose,D-xylose,L-arabinose,D-man-nose,L-fucose,D-galactose,D-glucuronic acid,D-galacturonicacid,D-mannuronic acid,N-acetyl-β-D-glucosamine). Calculation of the molar ratio of the monosaccharide was car-ried out on the basis of the peak area of the monosaccharide. Methylation AnalysisMethylation analysis was performed by the method of Hakomori(1964)with some modifications.In brief, 2mg of polysaccharide in dimethyl sulfoxide was meth-ylated using NaH and iodomethane,and the completion of methylation was confirmed by Fourier transform infrared (FTIR)spectroscopy by the disappearance of OH bands. After hydrolysis with2M trifluoroacetic acid at105°C for6h,the methylated sugar residues were converted to partially methylated alditol acetates by reduction with NaBH4,followed by acetylation with acetic anhydride. The derivatised sugar residues were extracted into dichlo-romethane and evaporated to dryness,and dissolved again in100μL of dichloromethane.The products were ana-lyzed by gas chromatography–mass spectrometry(GC-MS)on a DB225using a temperature gradient of100–220°C with heating at a rate of5°C/min and mainte-nance of a temperature at220°C for15min.GC-MS was performed on an HP6890II instrument.Identification of partially methylated alditol acetates was carried out on the basis of retention time and mass fragmentation patterns.IR Spectroscopy AnalysisFTIR spectra were measured on a Nicolet Nexus470spec-trometer.The polysaccharide was mixed with KBr powder, ground up,and then pressed into1-mm pellets for FTIR mea-surements in the frequency range of4000–500cm−1with a resolution of4.0cm−1and320scans co-addition.NMR Spectroscopy Analysis1H nuclear magnetic resonance(NMR)and13C NMR spectra were measured at23°C using a JEOL JNM-ECP600MHz spectrometer.60mg of polysaccharide was deuterium ex-changed by two successive freeze–drying steps in99%D2O and then dissolved in0.5mL of99.98%D2O.1H–1H corre-lated spectroscopy(COSY),1H–1H total correlation spectros-copy(TOCSY),1H–1H nuclear overhauser effect spectrosco-py(NOESY),1H–13C heteronuclear multiple quantum coher-ence spectroscopy(HMQC)and1H–13C heteronuclear multi-ple bond correlation spectroscopy(HMBC)experiments were also carried out.Chemical shifts are expressed in ppm using acetone as internal standard at2.225ppm for1H and 31.07ppm for13C.Analysis of Antioxidant ActivityScavenging ability of hydroxyl radicals was determined ac-cording to the method of Smirnoff and Cumbes(1989). Scavenging ability of superoxide radicals was assessed ac-cording to the method reported by Marklund and Marklund (1974).Scavenging ability of DPPH radicals was measured according to the method described by Shimada et al.(1992). The scavenging ability was calculated according to the equa-tion below:scavenging ability(%)=(1–A sample/A control)×100, where A control is the absorbance of control without the tested samples,and A sample is the absorbance in the presence of the tested samples.The EC50value(mg/mL)was the effective concentration at which the tested radicals were scavenged by 50%.Ascorbic acid was used as positive control in all anti-oxidant assays.All bioassay results were expressed as means ±standard deviation(SD).The experimental data were sub-jected to an analysis of variance for a completely random design,and three samples were prepared for assays of every antioxidant attribute.ResultsPreparation and Chemical Composition of the Extracellular PolysaccharideProcedures used for the preparation of the extracellular poly-saccharides from the fermented broth of the mangrove-associated fungus F.oxysporum were shown in Fig.1.Crude extracellular polysaccharide(0.59g/L)was obtained from the fermented broth,and fractionated using a Q Sepharose Fast Flow column(Fig.2a).The polysaccharide fraction,eluted with distilled water,was a major component of the crude polysaccharides.The fraction was further purified by a Sephacryl S-100column(Fig.2b),and a polysaccharide frac-tion Fw-1was obtained.The yield of Fw-1from crude polysaccharide was about 42.86%.Fw-1gave a single and symmetrical peak in the HPGPC chromatogram(Fig.2c),thus Fw-1could be a homo-geneous polysaccharide.The linear relationship between the logarithm of molecular weight of pullulan standards and re-tention time was obtained.The retention time in HPGPC chro-matogram of Fw-1was used to calculate its molecular weight by the obtained regression equation.Thus,the molecular weight of Fw-1was estimated to be about61.2kDa.Fw-1 contained91.3%total carbohydrate and minor amounts of protein(0.79%)and did not have any sulfate ester. Monosaccharide composition analysis by reversed-phase HPLC showed that Fw-1consisted of galactose,glucose, and mannose with a molar ratio of1.33:1.33:1.00.No acidic sugar and amino sugar were detected in Fw-1.Thepolysaccharide fraction Fs,eluted at 0.2M NaCl,was not further investigated due to the limit of sample amount.It is possible that fraction Fs contains an acidic polysaccharide,such as a polysaccharide with phosphate ester (Chen et al.2013).IR SpectroscopyFrom the FTIR spectrum of Fw-1,the broad and intense band at 3416cm −1was the result of valent vibrations OH groups.The signal at 2931cm −1was attributed to the stretch vibration of the C –H bond.The band at 1649cm −1was assigned to the bending vibrations of HOH,and the band at 1416cm −1originated from the bend-ing vibrations of O –H bond.The band at 1241cm −1was due to the stretch vibration of C –O –C linkages.The signal at 1032cm −1was assigned to the stretch vibration of C –O and change angle vibration of O –H.The characteristic ab-sorption bands at 876and 809cm −1suggested the pres-ences of furan ring and mannopyranose units,respectively (Ahrazem et al.2000;Mathlouthi and Koenig 1986).Methylation AnalysisIn order to determine the linkage pattern of the sugar residues,Fw-1was subjected to methylation analysis (Table 1).A large amount of 1,2,4,6-tetra-O -acetyl-3,5-di-O -methyl-galactitol,which originated from the (1→2,6)-linked galactofuranoseresidue,was detected in Fw-1,suggesting that Fw-1was a highly branched polysaccharide.1,5-di-O -acetyl-2,3,4,6-tet-ra-O -methyl-glucitol,1,2,5-tri-O -acetyl-3,4,6-tri-O -methyl-mannitol,and 1,2,5-tri-O -acetyl-3,4,6-tri-O -methyl-glucitol were also detected,indicating the presence of (1→)-linked glucopyranose,(1→2)-linked mannopyranose and (1→2)-linked glucopyranose residues.In addition,1,5-di-O -acetyl-2,3,4,6-tetra-O -methyl-mannitol,which originated from the (1→)-linked mannopyranose residue,was also found in Fw-1.The results suggested that the structure of Fw-1is com-posed of (1→2,6)-linked galactofuranose,(1→2)-linked glu-copyranose,(1→2)-linked mannopyranose,terminal gluco-pyranose,and mannopyranose residues.NMR SpectroscopyThe 1H NMR spectrum (Fig.3a )of Fw-1showed anomeric proton signals at 5.20,5.10,5.09,4.91,4.75,and 4.65ppm,which were labeled A –F from low to high field.The anomeric signals B and C almost overlapped.The anomeric proton sig-nals A –F had relative integrals of 1.0:0.5:0.5:0.25:0.25:0.25.A might be signal of β-galactofuranose residue.B and C were attributed to the signals of α-configuration pyranose units,and D –F were likely the signals of β-configuration pyranose units.The chemical shifts from 3.42to 4.26ppm were assigned to H2–H6of glycosidic ring.In the anomeric region of the 13C NMR spectrum (Fig.3b )of Fw-1,there were six main anomeric carbon signals that occurred at 107.8,102.4,101.8,101.3,99.6,and 99.5ppm.The anomeric carbon signal at 107.8ppm was due to signal of β-galactofuranose residue because of extremely low field shifts (Ahrazem et al.2006).As shown in the DEPT spectrum,the signal at 70.8ppm was assigned to the substituted C-6of β-galactofuranose units.The result confirmed the presence of the substituted C-6linkage patterns,which was in accordance to the methylation results.The 1H NMR spin systems chemical shifts of the polysac-charide were assigned by means of the 1H –1H COSY spec-trum (Fig.3c )and the 1H –1H TOCSY spectrum (Fig.3d ).Combined with the analysis of the 1H –13C HMQC spectrum of Fw-1(Fig.3e ),the observed 1H and 13C chemical shifts and the assignment of the sugar residues were given (Table 2).A was assigned to →2,6)-β-D -Gal f (1→because of the down-field chemical shifts of the C-2(88.1ppm)and C-6(70.8ppm).B and C were suggested to be Glc p because of the high field chemical shift of H-2(3.59and 3.69ppm).In the 1H –1H TOCSY spectrum,H-1of B and C showed the correlation peaks with H-2,H-3,H-4,and H-5,which con-firmed this speculation.The 1H –13C HMQC spectrum re-vealed the substitution of C at C-2due to the downfield chem-ical shift (77.0ppm)of C-2compared with the parent α-D -Glc p .Thus,B was attributed to α-D -Glc p (1→,and C was due to →2)-α-D -Glc p (1→.Combined with methylationanalysisFig.1Scheme for the preparation of the extracellular polysaccharide produced by the mangrove-associated fungus F .oxysporumand NMR spectra data (Takegawa et al.1997),E was assigned to →2)-β-D -Man p (1→because of C-2(78.0ppm)of E had a relative downfield chemical shifts.D and F were assigned to be β-D -Man p (1→,the different glycosidic bond and sugar rings,which linked with D and F,had different chemical en-vironments and chemical shifts.The sequence of glycosyl residues was determined from the 1H –1H NOESY spectrum,followed by confirmation with 1H –13C correlations obtained from the 1H –13C HMBC spec-trum.In the 1H –1H NOESY spectrum (Fig.3f )of Fw-1,A had a strong NOE contact of its H-1with the H-2of C,indicating C linked to the C-2position of A.B and C had a strongcontactFig.2Isolation and HPGPC chromatogram of the extracellular polysaccharide from the fermented broth of the mangrove-associated fun-gus F .oxysporum .a The crude polysaccharides were fractionated using a Q Sepharose Fast Flow column.The fraction eluted with distill water was pooled and named as Fw.b Fw was purified on a Sephacryl S-100column and eluted with 0.2M NH 4HCO 3.The peak fractions containing the polysaccharides were pooled and named as Fw-1.c HPGPC chro-matogram of Fw-1on a Shodex Ohpak SB-804column and the standard curve of molecular weightof its H-1with the H-2of A,suggesting B and C linked to theC-2position of A.D had a strong inter-residue contact be-tween its H-1and the H-2of E,indicating D linked to theC-2position of E.From the1H–13C HMBC spectrum ofFw-1(Fig.3g),the presence of strong cross peak H-1/C-4,C-6of A confirmed that A wasβ-galactofuranose configura-tion and→6)-β-D-Gal f(1→was the main pattern of linkage.The cross-peak H-1B,C/C-2A,and H-2A/C-1B,C indicatedthat B and C linked to the C-2of→6)-β-D-Gal f(1→.The 1H–13C HMBC spectrum of Fw-1also showed H-1F/C-2 C,H-1E/C-2C,H-1D/C-2E,H-2E/C-1D,B H-1/C-5crosspeaks,which further proved the existence ofβ-D-Man p(1→2)-β-D-Man p(1→2)-α-D-Glc p(1→andβ-D-Man p(1→2)-α-D-Glc p(1→.The results also revealed both the furanoid char-acter of A and the pyranoid structure of B–F.The NMR resultswere thus in agreement with methylation results.These anal-yses allowed the identification of most of the1H and13Csignals of the sugar residues.Thus,structure of Fw-1couldbe characterized to consist of the backbone of(1→6)-linked β-D-galactofuranose residues,with multiple branches at C-2 consisting of theα-D-Glc p(1→,β-D-Man p(1→2)-β-D-Man p(1→2)-α-D-Glc p(1→andβ-D-Man p(1→2)-α-D-Glc p(1→.The hypothetical structure of Fw-1was shown in Fig.4.Analysis of Antioxidant ActivityAs shown in Table3,the scavenging abilities of Fw-1on hydroxyl,DPPH,and superoxide radicals were in a concentration-dependent manner.Less scavenging of hydrox-yl radicals was observed with Fw-1at2mg/mL,but the scav-enging ability of Fw-1on hydroxyl radicals at10.0mg/mL was up to90.2%.Fw-1showed strong scavenging ability on hydroxyl radicals as evidenced by its low EC50value(1.1mg/ mL).The scavenging ability of Fw-1on superoxide radicals was50.2%at2.0mg/mL,and the scavenging ability of Fw-1 was up to89.2%at10.0mg/mL.The EC50value of scaveng-ing ability of Fw-1on superoxide radicals was2.0mg/mL. The scavenging ability of Fw-1on DPPH radicals was up to 88.2%at10.0mg/mL,and its EC50value was2.1mg/mL, indicating that Fw-1was also good effectiveness in the anti-oxidant attribute.The scavenging abilities of Fw-1on hydroxyl,superoxide and DPPH radicals were all relativelylower than that of ascorbic acid at the same concentrations. DiscussionA novel extracellular polysaccharide Fw-1is successfullyobtained from the mangrove-associated fungus F.oxysporum.Fw-1is an extracellular polysaccharidewith different structural characteristics from other extra-cellular polysaccharides produced by Fusarium sp.Thecell wall polysaccharides from F.oxysporum are com-posed of glucosamine and N-acetylglucosamine(Fukamizo et al.1992,1996),and the polysaccharidefrom Fusarium sp.M7-1consists of mannose,glucose,galactose,and glucuronic acid(Iwahara et al.1992).However,a small amount of→2)-β-D-Gal f(1→and→6)-α-D-Glc p(1→residues present in the cell wall polysac-charide of Fusarium sp.M7-1(Iwahara et al.1996).Somealkali-extractable and water-soluble extracellular polysac-charides from Fusarium species contain a backbone of β-(1→6)-linked galactofuranose residues almost fully branched at O-2by single residues of glucopyranose oracidic chains containing glucuronic acid and mannose.The extracellular polysaccharide from F.oxysporumY24-2is composed of→2)-β-D-Gal f(1→6)-α-D-Glc p(1→units(Guo et al.2013).The structure of Fw1also differs from othergalactofuranose-containing extracellular polysaccharides re-ported previously(Gómez-Miranda et al.2003;Leal et al.2010).The galactofuranans from Aspergillus niger, A.fumigatus,Trichophyton species and Penicillium charlesii,have been characterized as linear chains of(1→5)-linkedβ-D-galactofuranose units(Gander et al.1974;Latgéet al.1994; Unkefer and Gander1990;Ikuta et al.1997).For the extracel-lular polysaccharide from the deep-sea fungus P.griseofulvum,its galactofuranan chain consists of(1→5)-linkedβ-D-galactofuranose,with additional branches at C-6 consisting of(1→)-linkedβ-D-galactofuranose residues and phosphate esters(Chen et al.2013).Fw-1contains a backbone of(1→6)-linkedβ-D-galactofuranose residues with multipleTable1Results of methylation analysis of Fw-1Methylated sugar Primary mass fragments(m/z)Molar ratio Deduced linkage1,5-Di-O-acetyl-2,3,4,6-tetra-O-methyl-mannitol101,117,129,145,161,205 2.0Man p(→1,5-Di-O-acetyl-2,3,4,6-tetra-O-methyl-glucitol101,117,129,145,161,205 2.0Glc p(1→1,2,5-Tri-O-acetyl-3,4,6-tri-O-methyl-mannitol87,101,129,161,189 1.0→2)Man p(1→1,2,5-Tri-O-acetyl-3,4,6-tri-O-methyl-glucitol101,117,129,161,201,233,277 2.0→2)Glc p(1→1,2,4,6-Tetra-O-acetyl-3,5-di-O-methyl-galactitol87,101,117,129,173,189,201,233 4.0→2,6)Gal f(1→Fig.3NMR spectra of Fw-1.Spectra were performed at23°C on a JEOL ECP600MHz spectrometer Chemical shifts are expressed in ppm using acetone as internal standard at2.225ppm for1H and 31.07ppm for13C.a1H NMR spectrum.b13C NMR and DEPT spectra.c1H–1H COSY spectrum.d1H–1H TOCOSY spectrum.e 1H–13C HMQC spectrum.f1H–1H NOESY spectrum.g1H–13C HMBC spectrum.A→2,6)-β-D-Gal f(1→.Bα-D-Glc p(1→.C→2)-α-D-Glc p(1→.Dβ-D-Man p(1→,linked to→2)-β-D-Man p(l→.E→2)-β-D-Man p(l→.Fβ-D-Man p(1→,linked to→2)-α-D-Glc p(l→.Glcpglucopyranose,Manp mannopyranose,Galf galactofuranosebranches at C-2consisting of terminal α-glucopyranose resi-dues,or short chains containing (1→2)-linked α-D -glucopy-ranose,(1→2)-linked β-D -mannopyranose,and terminal β-D -mannopyranose residues.To the best of our knowledge,this is the first report of such kind of galactofuranose-containing mannoglucogalactan isolated from fermented broth of micro-organism.The present result suggested that mangrove-associated fungi could be a potential source of extracellular polysaccharides with unique structures to be worth being fur-ther studied.In order to investigate the antioxidant activity of Fw-1,the assays based on scavenging abilities of hydroxyl,superoxide,and DPPH radicals were carried out and compared with that of ascorbic acid,one standard antioxidant.Hydroxyl radical is considered to be a highly potent oxidant,which can react with most biomacromolecules functioning in living cells and in-duce severe damage to the adjacent biomolecules.In cellular oxidation reactions,superoxide radical is normally formed first,and its effects can be magnified because it produces hydrogen peroxide and hydroxyl radical through dismutationTable 21H and 13C chemical shifts for the extracellular polysaccharide Fw-1Sugar residuesChemical shifts (ppm)a H1/C1H2/C2H3/C3H4/C4H5/C5H6/C6A b 5.20/107.8 4.21/88.1 4.26/76.9 4.05/83.9 4.02/71.0 3.94,3.69/70.8B c 5.10/99.5 3.59/72.6 3.77/73.1 3.47/71.0 3.79/73.8 3.91,3.73/62.1C d 5.09/99.6 3.69/77.0 3.81/73.1 3.45/71.0 3.76/72.6 4.12,3.79/62.3D e 4.91/102.4 4.18/72.6 3.73/72.4 3.61/72.6 3.45/71.9 3.79,3.90/62.6E f 4.75/101.3 4.24/78.0 3.68/68.3 3.95/71.2 3.76/73.5 3.96,3.45/62.4F g4.65/101.84.02/71.93.73/72.43.96/71.13.80/73.63.47,3.86/62.3Glcp glucopyranose,Manp mannopyranose,Galf galactofuranoseaThe spectra were recorded using a JEOL JNM-ECP 600MHz spectrometer.Chemical shifts are referenced to internal acetone at 2.225ppm for 1H and 31.07ppm for 13C b →2,6)-β-D -Gal f (→c α-D -Glc p (1→d →2)-α-D -Glc p (1→e β-D -Man p (1→,linked to →2)-β-D -Man p (l →f →2)-β-D -Man p (l →gβ-D -Man p (1→,linked to →2)-α-D -Glc p (l→Fig.4One of the possible structures of Fw-1(Glcp gluco-pyranose,Manp ,mannopyranose,Galf ,galactofuranose,n ≈16)and other types of reaction and was the source of free radicals formed in vivo.DPPH is a useful reagent to evaluate the free radical scavenging ability of the hy-drogen donating antioxidant,which can transfer hydro-gen atoms or electrons to DPPH radicals.It was found that Fw-1had a more noticeable scavenging ability on hydroxyl radicals than the extracellular polysaccharide AVP produced by coral-associated fungus Aspergillus versicolor LCJ-5-4,and the EC50value of AVP was 4.0mg/mL(Chen et al.2012).Moreover,the scaveng-ing ability of Fw-1on superoxide radicals appears to be higher than that of the extracellular polysaccharide As1-1produced by marine fungi Aspergillus sp.Y16,and the EC50value of As1-1was 3.4mg/mL(Chen et al. 2011).Scavenging ability of Fw-1on DPPH radicals was similar to that of extracellular polysaccharide AVP produced by coral-associated fungus,A.versicolor LCJ-5-4,and its EC50value was2.05mg/mL(Chen et al. 2012).Fw-1had a higher scavenging ability on DPPH radicals than the extracellular polysaccharides PS2-1, PS1-2,and PS1-1isolated from marine fungus Penicillium sp.F23-2(EC50value 2.53–6.81mg/mL) (Sun et al.2009).The present result suggested that the extracellular polysaccharide Fw-1could be a potential antioxidant.The antioxidant activity of Fw-1may be attributed to the extracellular polysaccharide can connect with radicals,and terminate the radical chain reaction. However,the antioxidant mechanisms of polysaccha-rides are complex.Further study on antioxidant property of extracellular polysaccharides with different structural characterization will play an important role in the un-derstanding of the mechanism of antioxidant activity.In conclusion,the extracellular polysaccharide Fw-1pro-duced by the mangrove-associated fungus F.oxysporum is a galactofuranose-containing mannoglucogalactan differing from previously described extracellular polysaccharides.Fw-1exhibits good antioxidant activity in vitro.An in-depth investigation of the antioxidant activity of Fw-1will be re-quired to determine if the extracellular polysaccharide will be useful in the food and pharmaceutical industry. Acknowledgments This work was supported by the Science and Tech-nology Development Program of Shandong Province,China (2014GHY115015),NSFC-Shandong Joint Fund for Marine Science Re-search Centers(U1406402),and the National Oceanographic Center of Qingdao of China.ReferencesAhrazem O,Gómez-Miranda B,Prieto A,Barasoaín I,BernabéM,Leal JA(2000)An acidic water-soluble cell wall polysaccharide:a che-motaxonomic marker for Fusarium and Gibberella.Microbiol Res 104:603–610Ahrazem O,Prieto A,Giménez-Abián MI,Leal JA,Jiménez-Barberoa J, Bernabe M(2006)Structural elucidation of fungal polysaccharides isolated from the cell wall of Plectosphaerella cucumerina and Verticillium spp.Carbohydr Res341:246–252Bensadoun A,Weinstein D(1976)Assay of proteins in presence of in-terfering materials.Anal Chem70:241–256Bitter T,Muir HM(1962)A modified uronic acid carbazole reaction.Anal Biochem4:330–334Chen Y,Mao WJ,Tao HW,Zhu WM,Qi XH,Chen YL,Li HY,Zhao CQ, Yang YP,Hou YJ,Wang CY,Li N(2011)Structural characterization and antioxidant properties of an exopolysaccharide produced by the mangrove endophytic fungus Aspergillus sp.Y16.Bioresour Technol102:8179–8184Chen Y,Mao WJ,Yang YP,Teng XC,Zhu WM,Qi XH,Chen YL,Zhao CQ,Hou YJ,Wang CY,Li N(2012)Structure and antioxidant activity of an extracellular polysaccharide from coral-associated fun-gus,Aspergillus versicolor LCJ-5-4.Carbohydr Polym87:218–226 Chen Y,Mao WJ,Wang BF,Zhou LN,Gu QQ,Chen YL,Zhao CQ,Li N, Wang CY,Shan JM,Yan MX,Lin C(2013)Preparation and char-acterization of an extracellular polysaccharide produced by the deep-sea fungus Penicillium griseofulvum.Bioresour Technol132: 178–181Dubois C,Gilles KA,Hamilton JK,Rebers PA,Smith F(1956) Colorimetric method for determination of sugars and related sub-stances.Anal Chem28:350–356Table3Antioxidant activity of the extracellular polysaccharide Fw-1in vitroa The results were expressed as means±standard deviation(SD). The experimental data were subjected to an analysis of variance for a completely random design,and three samples were prepared for assays of every antioxidant attribute Sample Concentration(mg/mL)a0 2.0 4.0 6.08.010.0Scavenging ability on hydroxyl radicals(%)Fw-10.059.5±1.482.5±2.885.6±2.486.8±3.590.2±2.3 Ascorbic acid0.097.2±2.497.2±2.697.4±2.697.5±1.997.7±2.1 Scavenging ability on superoxide radicals(%)Fw-10.050.2±1.868.3±3.179.1±2.385.7±3.289.2±2.8 Ascorbic acid0.097.2±1.997.3±2.297.4±2.797.5±2.897.8±2.4 Scavenging ability on DPPH radicals(%)Fw-10.049.1±1.766.9±2.475.0±2.585.2±2.388.2±2.6 Ascorbic acid0.097.2±2.297.3±1.797.4±2.097.5±2.597.7±2.8。
固液界面反应法制备针状草酸钴粉体何显达;叶红齐;蒯勤;周永华;许开华【摘要】以钴粉和草酸(H2C2O4)为原料,采用固液界面反应法制备针状草酸钴(Co2C2O4·2H2O)粉体.用扫描电镜(SEM)、X射线衍射仪(XRD)和激光粒度仪对粉体进行表征,研究反应温度、钴粉浓度、草酸与钴粉的计量比以及无机酸的种类和用量对草酸钴粉体的形貌和长径比的影响.结果表明,反应温度为30℃时草酸钴粉体多为颗粒状;温度升高到70℃时,草酸钴针状粉体团聚严重;随反应物浓度增加,针状草酸钴粉体的长度有所减小;加入少量硝酸可使粉体长径比增大.在反应温度为50℃,草酸与钴粉的计量比(物质的量比)为2.5:1,硝酸添加量为0.05 mol/L的条件下,针状草酸钴粉体的长径比达40.【期刊名称】《粉末冶金材料科学与工程》【年(卷),期】2011(016)002【总页数】6页(P237-242)【关键词】针状草酸钴;钴粉;固液界面反应法【作者】何显达;叶红齐;蒯勤;周永华;许开华【作者单位】中南大学化学化工学院,长沙,410083;深圳市格林美高新技术股份有限公司,深圳,518116;中南大学化学化工学院,长沙,410083;中南大学化学化工学院,长沙,410083;中南大学化学化工学院,长沙,410083;深圳市格林美高新技术股份有限公司,深圳,518116【正文语种】中文【中图分类】TF123草酸钴是生产钴粉及其氧化物的传统原料[1-3]，最近的研究表明草酸钴也是性能优异的功能材料[4-5]。
草酸钴粉体通常由液相沉淀法制备[6-7]，该法用可溶性钴盐和草酸或草酸铵配制原料液，采取液液混合方式实现反应，具有工艺简单，反应快和成本低等优点。
然而，液相沉淀法制备的草酸钴粒径较大，且形貌不容易精确控制。
虽然添加表面活性剂[6]，采用固体加料方式[8]，引入脉冲电磁场[9]，利用微波辅助[10]，有助于减小粉体粒径；添加氯化铵[11]可以适当控制颗粒的形貌，但研究结果仍然不够令人满意，即在传统的液液混合条件下不易制得形貌可控的细颗粒粉体。
Accepted ManuscriptTitle: Preparation and characterization of core-shell structure Fe3 O4 /C nanoparticles with unique stability and high electrochemical performance for lithium-ion battery anode material Authors: Yudai Huang, Zhifang Dong, Dianzeng Jia, Zaiping Guo, Won Il Cho PII: DOI: Reference: To appear in: Received date: Revised date: Accepted date: S0013-4686(11)01214-X doi:10.1016/j.electacta.2011.07.141 EA 17550 Electrochimica Acta 23-4-2011 16-7-2011 31-7-2011Please cite this article as: Y. Huang, Z. Dong, D. Jia, Z. Guo, W.I. Cho, Preparation and characterization of core-shell structure Fe3 O4 /C nanoparticles with unique stability and high electrochemical performance for lithium-ion battery anode material, Electrochimica Acta (2010), doi:10.1016/j.electacta.2011.07.141 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.Preparation and characterization of core-shell structure Fe3O4/C nanoparticles with unique stability and high electrochemical performance for lithium-ion battery anode material Yudai Huang1,2,3, Zhifang Dong1,2,3, Dianzeng Jia1,2,3,*, Zaiping Guo4, Won Il Cho51Key laboratory of clean energy material and technology of ministry of education,2 3Key laboratory of advanced functional materials of autonomous region,Institute of Applied Chemistry, Xinjiang University, Urumqi 830046, Xinjiang, People’s Republic of China4Institute for Superconducting and Electronic Materials, University of Wollongong, Wollongong, NSW 2522, Australia5Ac ce p*Corresponding author. Tel.: +86-991-8583083; Fax: +86-991-8580032; E-mail: jdz0991@(D. Jia)teHawolgok-dong, Seongbuk-gu, Seoul 136-791, Republic of KoreaE-mail address: jdz0991@dEnergy Storage Research Center, Korea Institute of Science and Technology 39-1,M1anuscrip tPage 1 of 27Abstract: Core-shell structure carbon coating Fe3O4 nanoparticles are prepared by a two-step method. The crystalline structure and the electrochemical performance of the prepared samples are investigated. The results indicate that a uniform and continuousFe3O4/C nanoparticles show a high initial discharge capacity of 1546 mAh g-1 and aspecific stable discharge capacity of about 800 mAh g-1 at 0.5 C with no noticeable capacity fading up to 100 cycles.Keywords: Core-shell structure; Carbon coating; Fe3O4 nanoparticles; Lithium-ion battery; Anode materialAc ce pte2dManPage 2 of 27uscrip tcarbon layer is formed on the surface of Fe3O4 nanoparticles. The core-shell structure1. Introduction Lithium-ion batteries with high energy capacity have been successfully applied in portable electronic devices, electric vehicles, and implantable medical devices and sothe consumer: more efforts must be devoted to looking for new electrodes with highcapacity and long cycle life to meet the demands. The present commercial lithium-ion battery involves graphite anode, lithium cobalt oxide cathode, and liquid organic-solution electrolyte [4-6]. Improvement in performance can be obtained by replacing the conventional electrodes with others that possess higher specific capacity.theoretical capacities (500-1000 mAh g-1) of transition metal oxides are much higherwhich make them become promising anode materials for high performance lithium-ionAc ce pbatteries.In the past decades, Fe3O4 material has been widely investigated as ferromagnetic,biomedical, and catalysis application [6, 11, 12], and it also shows desirable properties as lithium-ion battery anode material [8]. The overall electrochemical reversible reaction is as follows:On deep discharge with Li, up to 0.01 V (vs. Li), as many as 8 moles of Li per mole of Fe3O4 react, its theoretical capacity is 924 mAh g-1, largely exceeds that of graphite (372 mAh g-1). However, the poor cycling performance of Fe3O4 is delaying its3tedthan that of graphitic carbon, and the volume change is not so great as silicon material,MThe preferable candidates for anode materials are transition metal oxides [7-10]. Theanuscrip tPage 3 of 27on for many years [1-3]. However, their performances still lie behind the demands ofpractical application. It suffers from limited lithium diffusion kinetics during the insertion/extraction electrochemical process. One of the promising ways to solve the problem is to disperse the material into a carbon matrix, where carbon acts as bothLi+ can easily intercalate into the framework of Fe3O4 through the partly graphiticcarbon shell [4, 5, 13-15]. Herein, a kind of novel composites of Fe3O4 nanoparticles encapsulated with carbon shell is prepared successfully through a two-step method. The carbon shell arises from carbonization of the polymer (bakelite). The electrochemical measurements show that the high initial discharge capacity of theC. Although the discharge and charge capacities slowly decay during the initial severalAc ce pother nanosized Fe-based materials reported by Liu et al. [7], Reddy et al. [9], and NuLi et al. [16], the cycling performance of the core-shell structure Fe3O4/Cnanoparticles was improved obviously. 2Experimental2.1. Preparation: The core-shell structure Fe3O4/C nanoparticles were preparedthrough a two-step method. Firstly, stoichiometric FeCl3 (A.R., Tianjinshengmiao, China) and NaOH (A.R., Tianjinshengmiao, China) were mixed with polyethylene glycol (PEG) 400 (A.R., Shanghaishanpu, China) (worked as dispersants) in an agate mortar and ground with a pestle for 1 h to make them react completely. Then theteg-1, and without noticeable capacity degradation up to 100 cycles. Compared withdcycles, a specific stable discharge capacity of the Fe3O4/C maintains about 800 mAhM4core-shell structure Fe3O4/C nanoparticles is 1546 mAh g-1 at the current density of 0.5anuscrip tPage 4 of 27structural buffer and electro-active material during the Li+ insertion/extraction process,mixtures were washed by distilled water and ethanol for several times, respectively. The obtained precursors were held at 120 for 10 h to get the Fe2O3 nanoparticles. Secondly, 0.1 mmol the as-prepared Fe2O3 and 0.5 mmol Cetyltrimethyl Ammoniumwater by ultrasonication to form a suspension, 0.1 mmol Resorcin (C6H6O2) (A.R.,Tianjintianxin, China) and excess Formaldehyde (CH2O) (A.R., Xi’anhuaxue, China) were added into the suspension, Na2CO3 (A.R., Tianjinshengmiao, China) was added as catalyst, then the mixture was refluxed 10 h at 90. After cooling to the room temperature, a red precipitation of polymer/Fe2O3 was collected by filtration, andCH2O. Ultimately, the polymer/Fe2O3 were dried and heat-treated at 450 for 2 hnanoparticles were obtained.Ac ce p2.2. Structure characterizationThe crystalline phase of the resulting materials wasanalyzed by powder X-ray diffraction (XRD, MXP18AHF, MAC, Japan), which was carried out using Cu Kα radiation (λ = 1.54056 Å). The grain size and morphology ofthe samples were observed using transmission electron microscopy (TEM, H-600, Hitachi, Japan) with an accelerating voltage of 100 kV. Fourier Transform Infrared Spectrum (FT-IR) of the samples was taken in KBr pellets by using a Bruker/VECTOR 22 FTIR spectrophotometer (Bruker Optics Inc, Germany). 2.3. Electrochemical characterization: The working electrodes were fabricated by mixing the as-prepared materials with acetylene black (AB) and poly(vinyldifluoride)tedunder argon atmosphere, and then the core-shell structure carbon coating Fe3O4/CM5washed several times by distilled water and ethanol to remove the excess Na2CO3 andanuscrip tPage 5 of 27Bromide (CTAB) (A.R., Tianjinshengmiao, China) were dispersed in 320 ml distilled(PVDF) at a weight ratio of 70:15:15 to form a slurry, then the slurry was pasted on pure Cu foil, the working electrodes were prepared. The prepared working electrode sheets were dried at 120 in a vacuum oven for 12 h. The electrochemical behavior ofelectrode, microporous polyethylene (Celgard 2400) as the separator, and 1 M LiPF6 in a mixture of ethylene carbonate (EC) and dimethylcarbonate (DMC) (1:1 by volume) as the electrolyte. The whole assembly process was carried out in an argon-filled glove box (Labstar P4173, M. Braun. Germany). Cyclic voltammogram (CV) was measured at a scan rate of 0.1 mV s-1 from 0.01-3.0 V using a CHI660B electrochemical(EIS) were conducted over the 0.01 Hz to 100 KHz frequency range using a Zahnerusing Z-view software (Version 2.2, Scribner Associates Inc., USA) to obtain theAc ce pNyquist plots. The discharge/charge cycling was performed within a voltage range of 0.01-3.0 V on a battery test instrument (CT2001A, Kingnuo, China) at ambient temperature.3. Results and discussionteThe core-shell structure carbon coating Fe3O4/C nanoparticles were prepared by reduction of the as-prepared Fe2O3 precursors. Firstly, the Fe2O3 nanoparticles weredElektrik electrochemical workstation (IM6e, Zahner, Germany). Data were analyzedMFig. 1 Fig. 2 Fig. 36workstation (CHI, 660B, Chenhua, China). Electrochemical impedance spectroscopiesanuscrip tPage 6 of 27the materials was examined via CR2032 coin-type cells with lithium metal as countersynthesized by solid-state method, and then the carbon precursor layers (bakelite) were coated on the outer surface of the Fe2O3 nanoparticles by the polymerization of C6H6O2 and CH2O with Na2CO3 as the catalyst. The mechanism of the polymerizationas-synthesized Fe2O3/polymer. It can be seen that the Fe2O3 nanoparticles with thediameter of about 80-100 nm are encircled by a uniform and continuous polymer layer. Fig. 3a and Fig. 3b show the powder X-ray diffraction (XRD) patterns of the Fe2O3/polymer and pure Fe2O3, in which all peaks of the both samples are in good agreement with α-Fe2O3 (JCPDS no. 33-0664), we can confirm that the structure ofSecondly, the products were heat-treated at 450 for 2 h under argon atmosphere toFe3O4 by the outer carbon layers during the calcining process, the final core-shellAc ce pstructure Fe3O4/C nanoparticles were obtained. Fig. 2b shows the TEM of the finalcore-shell structure Fe3O4/C composites. It can be seen that the Fe3O4 nanoparticleswith the diameter of about 80-100 nm are encircled by a uniform and continuous carbon layer. The Fe3O4 nanoparticles are physically isolated by the carbon matrix, any physical change of Fe3O4 nanopaticles can be restricted at its local region. The specialshell structure of carbon may decrease the volume change of core structure Fe3O4 during the electrochemical process availably. The small particles in Fig. 2b are the amorphous carbon, which are detached from the Fe2O3 nanoparticles surface during the calcining process. The XRD patterns of the Fe3O4/C are shown in Fig. 3c, in whichtedcarbonize the carbon precursor layers. The inner Fe2O3 nanoparticles were reduced toM7Fe2O3 before and after being coated do not change.anuscrip tPage 7 of 27is shown in Fig. 1. Fig. 2a shows the transmission electron microscopy (TEM) of theall peaks of the sample are coincident with the standard face-centered Fe3O4 (JCPDS no. 65-3107), which indicates that the Fe3+ are reduced during the heat-treated process, therefore, the final products can be identified with Fe3O4, which is further confirmedferromagnetism. No carbon peak can be observed from the Fig. 3c due to its amorphism and low content in Fe3O4/C nanocomposites. Fig. 4FTIR spectrum of the Fe2O3/polymer is presented in Fig. 4. The spectrum has the characteristic peaks of both Fe2O3 and the carbon precursors (bakelite). The peaks inFe2O3 [8, 17]. The main characteristic peaks of bakelite are assigned as follows: TheAc ce pand δ(C-H), respectively. On the basis of TEM, XRD and FTIR spectra, herein, we can further conclude that, bakelite have been formed on the surface of Fe2O3 nanoparticles. Fig. 5The electrochemical behaviors of the core-shell structure Fe3O4/C nanoparticleswere investigated by Cyclic Voltammetry (CV) and Galvanostatic Cycling. CV was measured at ambient temperature in the range of 0.01-3.0 V at a scan rate of 0.1 mV s-1 up to 5 cycles. The results are shown in Fig. 5, it is clear that the first cycle is substantially different from the subsequent cycles. In the cathodic polarization process of the first cycle, two obvious peaks are observed at 0.51 and 0.02 V, which could bete2927 cm-1, 2856 cm-1 and 1467 cm-1 are the characteristic peaks of νas(C-H), νs(C-H)dbroad band around 3380 cm-1 indicates the presence of hydroxy (OH). The bands ofM8the 400-800 cm-1 region are due to the multiple lattice absorptions of partially orderedanuscrPage 8 of 27ip tby the color change from red to totally black during heat treatment and strongattributed to the reaction Fe3O4 + 8Li+ +8e-3Fe0 + 4Li2O and 2C+Li+ +e-LiC2respectively [18, 19]. Meanwhile, in the anodic polarization process, a peak is recorded at about 1.65 V, corresponding to the reversible oxidation of Fe0 to Fe3O4. In theand the integrated areas of the peaks decreased gradually during the initial five cycles, indicating the irreversible capacity loss in the initial several cycles. Fig. 6Galvanostatic discharge/charge experiments were carried out to evaluate the electrochemical performance of the core-shell Fe3O4/C nanoparticles. Theof 0.5 C up to 100 cycles in the voltage range of 0.01-3 V at the ambient temperature.in Fig. 6a, Fig. 6b, Fig. 6c and Fig. 6d, respectively. The open-circuit voltage (OCV) ofAc ce pthe fabricated and aged cells (12 h) is about 1.9 V, in the first discharge cycle, the voltage decreases steeply to 0.7 V, where a plateau sets in and continues until a capacity of about 693 mAh g-1 (x=6) [16, 20, 21], followed by a gradual drop in voltage until the end of discharge. In the 100th discharge cycle, the voltage plateau is about 0.75V. The plateau voltages are clearly reflected as peaks in the differential capacity versus voltage plots, which are shown in Fig. 6e and Fig. 6f. The total initial discharge capacity of the Fe3O4/C is about 1546.4 mAh g-1 (x=13.4), the extra capacity of the Fe3O4/C beyond the theoretical values is probably due to the decomposition of non-aqueous electrolyte during the discharge process [22, 23]. In the 2nd cycle, thetedThe results of the 1st, the 2nd, the 3rd and the 100th discharge/charge curves are shownM9discharge/charge curves of the core-shell Fe3O4/C nanoparticles were obtained at a rateanuscrPage 9 of 27ip tsubsequent cycles, the curves differ considerably from the first; both the peak currentsA cc ep te dMa nu sc ri p tspecial discharge capacity of the Fe 3O 4/C is 901.4 mAh g -1(x=7.8), which is very close to its theoretical capacity (924 mAh g -1), indicating the Fe 3O 4/C possesses excellent electrochemical performance.The second discharge curves of the core-shell Fe 3O 4/C nanoparticles is differentfrom the first, suggesting drastic, lithium-driven, structural or textural modifications[10, 24]. Furthermore, the charge voltage plateau of the core-shell Fe 3O 4/C nanoparticles is higher than the discharge. The large polarization (i.e., voltage hysteresis between charge and discharge) could be due to the poor conversion reaction kinetics (limited lithium diffusion kinetics during the intercalation/de-intercalationprocess, for example) of the core-shell Fe 3O 4/C nanoparticles [11, 24, 25]. Thephenomenon of polarization has been widely observed in a number of other Fe 3O 4–Ccomposites [13, 14, 26-29]. Unfortunately, the large polarization strongly penalizes theenergy efficiency of lithium-ion batteries. Therefore, it is very important to reduce the polarization of the core-shell Fe 3O 4/C nanoparticles in the future work by improvingthe conversion reaction kinetics, such as reducing the particle size of the core-shellFe 3O 4/C nanocomposites [24].However, the core-shell Fe 3O 4/C nanoparticles showed an initial discharge capacity(lithiation) of 1546.4 mAh g -1 and charge capacity of 806.3 mAh g -1 in the first cycle.Large irreversible capacity observed in the first cycle may be caused by the conversion of Fe 3O 4 to Fe nanoparticle and the formation of amorphous Li 2O, trapped Li + in the inner holes of the core-shell Fe 3O 4/C nanoparticles and the formation of solid electrolyte interphase (SEI)[27, 30].A c c e p t e d M a n u s c ri p tA cc ep te dMa nu sc ri p tstructure, which involves Fe 3O 4 nanoparticles in a protective carbon matrix.The Fe 3O 4/C nanoparticles benefit from an excellent stability since the nanoparticles can be stored in open air without undergoing any decomposition [4], moreover, the Fe 3O 4crystallites are connected with a carbon shell, which thereby further ensure theelectrical continuity around the crystallites [15].Fig. 8Information that surface film formation, factors governing the cycling stability such as charge-transfer resistance, bulk resistance and Li + kinetics can be obtained through electrochemical impedance spectral (EIS) studies on electrode materials at variousvoltages during cycling. In the present study, to understand the reasons for theobserved differences in the cycleability of the core-shell structure Fe 3O 4/Cnanoparticles, impedance measurements were carried out at room temperature, and theimpedance spectra obtained during the 1st and 100th cycles for a given electrode at different states of discharge and charge are given in Fig.8. The impedance data wereanalyzed using Z-view software by fitting to an equivalent electrical circuit composedof R i (bulk resistance); CPE i (due to the depressed semicircle observed in the spectra);a Warburg impedance (W s ); and the intercalation capacity (C int ), shown in Fig.9,similar to the circuit employed for other oxide electrodes [9, 17, 31]. The symbols are the experimental data whereas the continuous lines represent the fitted spectra.A fresh cell of Fe 3O 4/C versus Li with an OCV of 1.28 V shows a single depressed semicircle in the high frequency region and a Warburg-type behavior in the low-frequency region. Curve fitting gives an impedance of 250Ω which is attributedA cc ep te dMa nu sc ri p tto a combination of the surface film formation and the charge-transfer resistance (R ct ), the associated CPE is 17μF. During the first discharge cycle, shown in Fig.8a, the R ct falls to the lowest value of 95 Ω at voltage of 0.8 V . W ith the discharge process, thespectrum shows a slightly sloping behavior in the low-frequency region, the act showsthe onset of bulk impedance. In the first charge cycle, shown in Fig.8c, a single depressed semicircle followed by the Warburg region is observed, which indicates acontribution only from R ct , the fitted values of R ct at voltage of 0.16 V is 126 Ω, and maintain 195±5Ω subsequently. After 100 discharge/charge cycles, the same test was carried out, as Fig.8b and 8d show.It can be seen that the plots of both discharge andcharge process are similar to each other in shape with a single semicircle appearing inthe high frequency and a straight line in the low frequency region, the fitted data areshown in table 1.The impedance spectra during the 100th discharge cycle are shown inFig.8b. The calculated values of R ct and CPE go through a minimum of 125 Ω, 11 μF , respectively. The impedance spectra during the 100th charge cycle are shown in Fig.8d. The calculated values of R ct and CPE go through a minimum of 122 Ω, 34 μF , boththe R ct and CPE values during the 100th cycle vary slightly from the 1st cycle,indicating a stable electrochemical process.Fig. 9Table14. ConclusionsFe 3O 4 nanoparticles are easily encapsulated in carbon, and formed core-shellA cc ep te dMa nu sc ri p tstructure carbon coating Fe 3O 4 nanocomposites.The electrochemical measurements demonstrate that the core-shell structure Fe 3O 4/C nanoparticles exhibit stable discharge capacity of about 800 mAh g -1 with no noticeable capacity fading up to 100cycles,which is much higher than the theoretical discharge capacity of the commercialgraphite.It indicates that the method that dispersing Fe 3O 4nanoparticles into carbon matrix is an effective way to improve the cycling performance of lithium-ion battery anode materials.AcknowledgementsThis work was supported by the Nature Science Foundation of Xinjiang Province(200821121), the National Natural Science of China (20866009 and 20861008),Technological People Service Corporation (2009GJG40028), the Science andTechnology Foundation of Urumqi (y08231006 and ZD8113007) and the Science andTechnology Foundation of Xinjiang University (BS100114 ).References[1]X. 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Scheme of the resorcinol-formaldehyde formation mechanismA cc ep te dMa nu sc ri p tFig. 2. TEM of (a) Fe 2O 3/polymer; (b) core-shell structure Fe 3O 4/C nanoparticlesA cc ep te dMa nu sri p tI n t e n s i t y /a .u .2-Theta/degreeFig. 3. XRD patterns of (a) the bare Fe 2O 3 nanoparticles; (b) the Fe 2O 3/polymer; (c) core-shell structureFe 3O 4/C nanoparticlesA cc ep te dMa nu sc ri p t4000350030002500200015001000500Wave number/cm-1T r a n s m i t t a n c e3380292728531598146712261095570Fig. 4. FTIR spectrum of the Fe 2O 3/polymerA cc ep te dMa nu sc ri p t0.00.51.01.52.0 2.53.0-0.6-0.5-0.4-0.3-0.2-0.10.00.10.2C u r r e n t /m AVoltage/V1st2nd3rdFig. 5. Cyclic voltammogram of the initial 5 cycles of the core-shell structure Fe 3O 4/C nanoparticleste Mc ri 02314626939241155138616170.00.51.01.52.02.53.00141210642Li x Fe 3O 4V o l t a g e /VCapacity/mAh g -18023*******9241155138616170.00.51.01.52.02.53.0Capacity/mAh g-1V o l t a g e /V141210642Li x Fe 3O 482314626939241155138616170.00.51.01.52.02.53.0Capacity/mAh g -1V o l t a g e /V0141210642Li x Fe 3O 4802314626939241155138616170.00.51.01.52.02.53.0Capacity/mAh g-1V o l t a g e /V141210642Li x Fe 3O 480.00.51.01.52.0-15000-10000-50005000d q /d V /m A h g -1V-1Voltage/V -1500-1000-500d q /d V /m A h g -1V-1Fig. 6. Galvanostatic discharge/charge curves of the core-shell structure Fe 3O 4/C nanoparticles in the voltage range 0.01-3.0 V (vs. Li) at a current density of 0.5 C. (a)1st, (b) 2nd, (c) 3rd, (d)100th; (e) the 1st discharge cycle, and (f) the 100th discharge cycle differential capacity, dq/dV(mAh g -1V -1), versus voltage (V) plots extracted from (a) and (d), respectively.A cc eu sc ri p t2004006008001000120014001600020406080100C a p a c i t y /m A h g-1Cycle numberE f f i c i e n c y /%C a p a c i t y /m A h g-1Cycle numberFig. 7. Cycling performance of (a) the core-shell structure Fe 3O 4/C nanoparticles, and (b) commercial Fe 3O 4 in the voltage range of 0.01-3.0 V at a current density of 0.5 CA cnu st010*******400100200300400-Z i m /o h mZ re /ohm100200300400100200300400-Z i m /o h mZ re /ohm。
